The present invention relates to drywall finish trim devices typically utilized in finishing a drywall installation at a corner or terminus.
Drywall, sometimes also referred to as wallboard, is a staple in the construction industry as an economical alternative to joint compound for forming the interior walls and ceilings of rooms in residential, commercial, and industrial buildings. The materials used in drywall construction include gypsum board, plywood, fibre-and-pulp boards, and asbestos-cement boards. The large, rigid sheets are fastened directly to the frame of a building with nails, screws, or adhesives, or are mounted on furring (strips of wood nailed over the studs, joists, rafters, or masonry, which allow free circulation of air behind the interior wall). A significant advantage afforded by drywall construction is that it allows a builder to avoid the unnecessary delays attendant to the drying of wet plaster before other work can be started or before the on site work required to achieve specific finishes may be completed. Wallboard is manufactured in both finished and unfinished forms, and finished wallboards may be faced with vinyl or other materials in a variety of permanent colors and textures so that they do not need to be painted when installed.
When employing drywall in construction, builders can easily cut the panels to any desired shape and size. However, workmen face a challenge in finishing drywall panels at an edge or corner. It is very difficult, if not impossible, to cut the edges of such panels with the precision, straightness, and smoothness that is required so that the abutted edges of adjoining panels form a straight corner that will afford an aesthetic finish. Additionally, cutting of the drywall panels exposes the soft, raw cores thereof, thus requiring some sort of covering to provide a finished appearance.
As a result, to cover drywall panel edges and enhance the aesthetics of a drywall joint, several devices and techniques may be employed in an effort to produce a structurally sound corner that will exhibit a smooth and seamless intersection. Devices proposed to achieve this result include drywall tape, trim and corner beads. When conventional drywall tape is used, it is applied to the joints and edges of abutting panels and is covered with wet joint compound that is feathered and smoothed to cover the newly created seams. When the joint compound has dried, the tape and drywall can be sanded, painted, covered, or otherwise finished in whatever manner is desired. A great deal of skill is required, however, to apply and form the joint compound to create a sufficiently straight intersection that will not exhibit, when taped and sanded to a finish, evidence of scuffing and tearing in the body of the tape.
In light of the limitations of drywall tape, trim strips or corner beads are often utilized in effort to produce a seamless and aesthetically pleasing edge trim or intersection at the corners of drywall panels.
Such trim may take many different forms such as a flat strip, a corner bead having flanges diverging at any one of a number of different angles, or a J strip to cap the edge of a dry wall panel. For the purposes of this invention, the particular angular configuration is not critical, but use in conjunction with numerous different configurations presently in existence and that may be developed in the future is contemplated. Further examples of corner trims include beads with perpendicular flanges, corner trims with a rib formed at the juncture of the flanges, flanges angled at 135° to one another, those configured with somewhat of a Z shape, those with soft line corners, and those with offsets or other configurations traditionally used in the trade and known to those skilled in the art.
To enhance the finished appearance of construction finished drywall with such trim, efforts have been made to cover a hard structural core with an exterior covering of paper or paper like material to enhance the finished appearance. It is recognized that by covering a plastic or metal core with paper, the paper will serve to cooperate with the covering on adjacent drywall panels to, when covered with a joint compound, afford a continuous smooth appearance from such panels and over the resultant trimmed joint. The compound may be sanded down and feathered in effort to provide a continuous smooth surface.
A disadvantage arising from the use of such paper covered trim cores is that during the sanding process, the workman sometimes sands through such compound and into the paper layer. This sanding tends to scuff up the fiber in the paper layer leaving somewhat of a scuffed or abraded surface, oftentimes with frayed fiber ends. This results in a discontinuous and unattractive surface. Efforts to solve this problem have led to the development of various different trims and corner beads that incorporate a protective layer constructed of either a strengthening compound or paper impregnated at the outer surface.
While these advancements may act to provide some strengthening to the covering paper, there remains a problem with portions of the paper being raised relative to other portions so as to expose the surfaces of these raised portions to being sanded away during the sanding operation resulting in an irregular finish appearance. From my examination of various samples and experimentation of production line product, I have discovered that a principal problem is not in the strength of the paper. Rather, it is the lifting up of the paper and consequent unevenness of the exposed surface. From my experimentation, I have discovered that the problem often lies in the breaking of the bond between the paper and the core, typically in an area where the core surface is recessed or there is some other irregularity. By experimentation, I have discovered that when subjected to high temperatures at low humidity stock paper shrinks. Shrinkage of the paper relative to the core results in the forces generated by such contraction that overcome the bond strength in certain areas thus leading to localized separation of the paper from the core. Then when the trim is exposed to higher humidity's, the paper will absorb moisture tending to expand longitudinally resulting in the paper tending to buckle up in the areas where the bond has been broken leading to localized bubbling up and resulting in the high surfaces which are prone to be sanded away during the finishing process. The problem is compounded by the fact that until the paper is rehydrated, often after installation is about to be or has been initiated, the problem is often not manifested. In practice this issue becomes especially evident when trim strips or beads are subjected to high temperatures above 100° F., as during storage in sheds, during transportation, or after prolonged exposure to various environmental conditions. In such instances, the paper covering will often shrink and bubble up on the core or pull away from it, particularly in any areas of any irregularity such as adjacent any shoulder or rib formed in such core. This bubbling and separation of the paper covering is often detected only at the construction site after the product has been transported and stored for preparation of the drywall phase of the construction project. Consequently, the onsite workmen oftentimes reject and discard any strips which appear to be affected with such deteriorated trim resulting in significant waste of both product and time.
Consequently, there exists a need for a durable, affordable, and aesthetically pleasing corner bead device having a paper covering not susceptible to shrinkage or rupturing at elevated temperatures or after prolonged exposure to the environment.